The present invention relates to a method of manufacturing a multi-metal layer semiconductor device with improved hot carrier injection reliability. The invention has particular applicability in manufacturing high density multi-metal layer semiconductor devices with design features of 0.25 micron and under.
The escalating demands for high densification and performance associated with ultra large scale integration semiconductor devices require design features of 0.25 micron and under, such as 0.18 micron, increased transistor and circuit speeds, high reliability and increased manufacturing throughput. The reduction of design features to 0.25 micron and under generates numerous problems challenging the limitations of conventional technology, including conventional photolithographic, etching, and deposition techniques.
Conventional methodology for forming patterned metal layers, as part of xe2x80x9cback-endxe2x80x9d wafer processing, comprises a subtractive etching or etch back step as the primary metal patterning technique. Such methodology involves the formation of a first dielectric interlayer on a semiconductor substrate, typically doped monocrystalline silicon, with conductive contacts formed therein for electrical connection with an active region in or on the semiconductor substrate, such as a gate oxide or a source/drain region. A metal layer, such as aluminum or an aluminum alloy, is deposited on the first dielectric layer, and a photoresist mask is formed on the metal layer having a pattern corresponding to a desired conductive pattern. The metal layer is then etched through the photoresist mask to form the conductive pattern comprising metal features separated by gaps, such as a plurality of metal lines with inter wiring spacings therebetween. A dielectric material, such as spin-on glass (SOG) is typically deposited to fill in the gaps between the metal features and baked at an elevated temperature. The baking time is determined depending upon the particular material employed. Thereafter, another dielectric layer is deposited thereover, such as a silicon oxide derived from tetraethyl orthosilicate (TEOS) by plasma enhanced chemical vapor deposition (PECVD). Planarization, as by chemicalmechanical planarization (CMP), is then performed.
The drive to increased density and attendant shrinkage in feature size generates numerous problems. For example, as feature sizes, e.g., metal lines and interwiring spacings, shrink to 0.50 micron and below, such as 0.375 micron, it becomes increasingly difficult to satisfactorily voidlessly fill in the interwiring spacings with a dielectric material and obtain adequate step coverage.
Hydrogen silsesquioxane (HSQ) offers many advantages for use in back-end wafer processing. HSQ is relatively carbon free, thereby rendering it unnecessary to etch back HSQ below the upper surface of the metal lines to avoid poisoned via problems. In addition, HSQ exhibits excellent planarity and is capable of gap filling interwiring spacings less than 0.30 micron while still employing conventional spin-on equipment. HSQ undergoes a melting phase at approximately 200xc2x0 C., but it does not convert to the high dielectric constant glass phase until reaching temperatures of about 400xc2x0 C. in intermetal applications. As deposited, HSQ is considered a relatively low dielectric constant (xe2x80x9clow kxe2x80x9d) material with a dielectric constant of about 2.9-3.0, compared to silicon dioxide grown by a thermal oxidation or chemical vapor deposition which has a dielectric constant of about 3.9-4.2. The mentioned dielectric constants are based on a scale wherein 1.0 represents the dielectric constant of air.
Other hydrogen containing low dielectric constant materials suitable for use as gap filling and/or cap layers in back-end wafer processing include but are not limited to methyl silsesquioxane (MSQ) and other organic low k materials.
However, in attempting to apply a hydrogen-containing low k material, such as HSQ, to xe2x80x9cback-endxe2x80x9d wafer processing as described above, particularly for gap filling, it was found that the hydrogen contained therein undesirably diffuses into the underlying dielectric interlayer during its deposition and/or during subsequent processing. Such hydrogen diffusion into the dielectric interlayer overlying active device regions formed in or on the substrate adversely affect hot carrier injection reliability which, in turn, reduces or deleteriously affects device performance.
In addition, deleterious hydrogen diffusion into the dielectric interlayer may also result upon formation and/or subsequent processing of a hydrogen containing oxide xe2x80x9ccapxe2x80x9d layer typically deposited over the dielectric layer prior to metal pattern formation and gap filling.
There exists a need for semiconductor technology enabling the use of low dielectric constant gap fill layers, such as HSQ, without adverse impact on hot carrier injection reliability.
An advantage of the present invention is a method of manufacturing a high density, multi-metal layer semiconductor device with improved hot carrier injection reliability.
Another advantage of the present invention is an improved method for xe2x80x9cback-endxe2x80x9d processing of a semiconductor wafer comprising active device regions therein.
Still another advantage of the present invention is a method for reducing or preventing diffusion of hydrogen into a dielectric interlayer as a result of subsequent formation of hydrogen-containing dielectric layer(s) thereon.
A still further advantage of the present invention is a semiconductor comprising a low k gap fill layer with high hot carrier injection reliability.
Additional aspects, advantages and other features of the present invention will be set forth in part in the description which follows and, in part, will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the invention. The aspects and advantages of the invention may be realized and obtained as particularly pointed out in the appended claims.
According to the present invention, the foregoing and other aspects and advantages are achieved, in part, by a method of manufacturing a multilevel semiconductor device, which method comprises: forming a dielectric interlayer on a substrate; treating the exposed upper surface of the dielectric interlayer with nitrogen to form a nitrided barrier layer thereon; and forming at least one hydrogen-containing dielectric layer over the nitrided barrier layer, wherein the nitrided barrier layer prevents diffusion of hydrogen from the at least one hydrogen-containing dielectric layer into the dielectric interlayer.
A further aspect of the present invention is a method of manufacturing a multilevel semiconductor device which comprises: forming a dielectric oxide interlayer on a substrate comprising a semiconductor; treating the exposed upper surface of the dielectric oxide interlayer with nitrogen to form a nitrided barrier layer thereon; forming an oxide cap layer on the nitrided barrier layer; forming a patterned metal layer on the oxide cap layer, the patterned metal layer having metal features spaced apart by gaps; and depositing a layer of low dielectric constant material on the patterned metal layer filling the gaps, wherein at least one of the oxide cap layer and the low dielectric constant material layer contains hydrogen, and the nitrided barrier layer formed on the dielectric oxide interlayer prevents diffusion of hydrogen from the at least one hydrogen containing layer into the dielectric oxide interlayer.
In another aspect of the present invention, the dielectric oxide interlayer comprises silicon oxide, the exposed surface of the dielectric oxide interlayer is treated to form a nitrided barrier layer by implanting nitrogen ions thereinto, the oxide cap layer comprises a silicon oxide derived from silane (SiH4) or tetraethyl orthosilicate (TEOS) under plasma conditions, and the layer of low dielectric constant material comprises hydrogen silsesquioxane (HSQ).
Another aspect of the present invention is an improved semiconductor device comprising: a semiconductor substrate having at least one active device region on or within said substrate; a dielectric oxide interlayer formed on the substrate over the at least one active device region; a patterned metal layer on the oxide cap layer, the patterned metal layer having metal features spaced apart by gaps; a layer of low dielectric constant material on the patterned metal layer and filling the gaps therein, wherein at least one of the oxide cap layer and the low dielectric constant material layer contains hydrogen; and a nitrided barrier layer formed on the surface of the dielectric oxide interlayer at the interface with the oxide cap layer which prevents diffusion of hydrogen from the at least one layer containing hydrogen into the dielectric oxide interlayer.
In a further aspect of the present invention, the semiconductor substrate comprises silicon, the dielectric oxide interlayer comprises a silicon oxide, the oxide cap layer comprises a silicon oxide derived from silane (SiH4) or tetraethyl orthosilicate (TEOS) under plasma conditions, and the layer of low dielectric constant material comprises hydrogen silsesquioxane (HSQ).
Additional aspects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive.